Mesophyll cell‐sucking herbivores ( C icadellidae: T yphlocybinae) on rainforest trees in Papua N ew G uinea: local and regional diversity of a taxonomically unexplored guild

Host specificity of a guild of sucking insects tapping leaf mesophyll cells ( A uchenorrhyncha: T yphlocybinae) was surveyed for the first time in the tropics, on 65 woody species from a lowland rainforest in P apua N ew G uinea ( PNG ). Typhlocybinae species were host specific, feeding on 1–3 (median 1) plant species. Their assemblages did not functionally connect populations of different plant species, as an overwhelming majority (> 99%) of tree species pairs coexisting in the same forest did not share any typhlocybine species. Cell‐sucking typhlocybines were more specialised than phloem‐ and xylem‐sucking A uchenorrhyncha. Typhlocybines were also more specialised in PNG than on trees in temperate E urope, even after standardisation for different phylogenetic diversity of tropical and temperate trees. The cell‐sucking guild was species poor, with 0–5 (median 1) typhlocybine species per tree species. Their distribution among tree species conformed to a P oisson distribution, suggesting that tropical typhlocybine assemblages are not saturated with species. Early succession plants supported a higher number of typhlocybine species than primary forest hosts but this preference could not be explained by successional trends in specific leaf area, foliar nitrogen content, wood density, tree abundance, or tree size. The effective specialisation of typhlocybines on 65 plant species E = 0.79 was extrapolated to the entire known flora of PNG and used to estimate that there may be at least 2775 typhlocybine species in PNG , in comparison to the global total of only 4508 taxonomically described species, including merely 40 from PNG .